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U. S. Meat Animal Research Center, U. S. Department of Agriculture, Clay Center, NE 68933
Abstract
Growth, puberty and pregnancy were studied in 665 crossbred heifers produced by breeding Hereford and Angus cows to Hereford, Angus, Red Poll, Brown Swiss, Gelbvieh, Maine Anjou, and Chianina sires. Estrus was determined from an average of 240 to 476 days of age. Puberty age was defined as age at first observed, standing estrus followed by an estrus within 45 days, except during the last 45 days of estrus detection when it was defined as first standing estrus. Heifers were bred by artificial insemination for 42 days and naturally for 22 days from an average age of 412 to 476 days.
Brown Swiss, Gelbvieh, Maine Anjou and Chianina crosses were 5 to 7% heavier (P<.01), while Red Poll crosses were not different (P>.05) from the Hereford-Angus crosses at the 200-day weight. Compared to Hereford-Angus crosses at 400 days of age, Maine Anjou, Chianina and Gelbvieh crosses were 5 to 8% heavier( (P<.01), Red Poll crosses were 4% lighter (P<.01), and Brown Swiss were 3% heavier (P>.05).
Sire breed influenced (P<.01) puberty age and percentage of heifers reaching puberty by 270 to 450 days of age. Sire breed groups divided into three groups for puberty age with Gelbvieh (343 ± 5), Brown Swiss (349 ± 4), and Red Poll (354 ± 5) crosses the youngest (P<.01), Chianina (401 ± 5) crosses the oldest (P<.01), and Maine Anjou (374 ± 5) and Hereford-Angus (374 ± 5) crosses intermediate. Chianina crosses were heaviest at puberty (319 ± 4 kg); followed by Maine Anjou crosses (307 ± 4); then Gelbvieh (286 ± 4 kg), Hereford-Angus (284 ± 4), and Brown Swiss (281 ± 3) crosses; with Red Poll crosses (265 ± 3) the lightest.
The heritability estimate was .41 ± .17 for puberty age, .40 ± .17 for puberty weight, and the genetic correlation between puberty age and puberty weight was .52 ± .23. Using breed group means, the correlations between puberty age and the following traits were: birth weight (.66), puberty weight (.90), calving as 2-year-olds the first 25 days of the calving period (–.75), percentage pregnant (–.42), milk production as 3- and 4-year-old cows (–.88), and percentage fat trim at a constant age of steer contemporaries (–.70).
1 Cooperation of the Nebraska Agricultural Experiment Station, University of Nebraska, Lincoln, is acknowledged. Authors express appreciation to Larry G. Beerwinkle, Gordon Hays, Charles DeGeer, John Stark, Melvin Sukup, Robert DeGunia and Richard Iverson for data collection, and to Wayne Hinerman and Bradford Knapp, Jr. for statistical analyses.
2 Science and Education Administration, Agricultural Research.
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